Page 106 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

LESSON 56-63 : Uninterrupted power supply (UPS)

Objectives

At the end of this lesson you shall be able to:
• explain the operative principles as UPS
• differentiate between UPS & Invertor
• advantage & disadvantage of UPS.

Concept of Uninterrupted Power Supply
An uninterruptible power supply (UPS) is a type of device that powers equipment, nearly instantaneously, in the
event of grid power failure, protecting the equipment from damage.
UPS systems vary significantly in their design and functionality, affecting the amount of time they can power
equipment, their ability to improve power quality, and their cost.
Data servers, computer systems, industrial settings, and laboratories commonly use UPS systems. Because
a UPS protects equipment, it is appropriate for any situation where electrical loads may be sensitive to power
loss or other power quality issues. For example, UPS systems are commonly used for computers and servers
because power loss to these loads may result in loss of data or component damage.
The UPS finds wide applications as a reliable power source to computer, telex and fax system and where
continuous regular and stable power supplies are required. The major users of UPS are the industries, business
houses/ establishments, hospitals, banks, offices, cinema theatres, railway stations and hotels etc. The UPS
consists of a battery charger, an inverter, output transformer, a set of batteries, control circuits and transient/ EMI
filters.
Major Parts of an UPS:
Following are the main components of a UPS system −

Battery - The battery works as the energy storage unit in the UPS system. It provides the stored electrical energy
for a sufficient amount of time during main power failure.
Rectifier or Charger Circuit - It converts the supply voltage of 240 VAC into 12 V (or any other battery voltage)
DC. It supplies this rectified DC power to the battery for storage.
Inverter - It converts the DC output power of the battery into ac power to supply the load during mains power
failure.

Static Switch - It is a semiconductor device such as a thyristor which transfers the load from the utility to the
inverter (and the inverter to the utility) without any interruption in the power supply to the load.
INVERTER

A power inverter, inverter, or invertor is a power electronic device or circuitry that changes direct current (DC)
to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed.
Inverters do the opposite of rectifiers which were originally large electromechanical devices converting AC to DC.
The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific
device or circuitry. The inverter does not produce any power; the power is provided by the DC source.

A power inverter can be entirely electronic or maybe a combination of mechanical effects (such as a rotary
apparatus) and electronic circuitry. Static inverters do not use moving parts in the conversion process.
Difference between UPS and Inverter

The following table highlights the key differences between a UPS and an inverter

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